Making key lifestyle changes following diagnosis of a chronic health condition is critical to improving quality of life and extending longevity. There have been few studies of long-term changes in health behavior following illness and little investigation into the pre-existing factors that may be associated with lifestyle improvements, however. The proposed study will investigate the following aims in two long-term longitudinal health studies, the Health and Retirement Study (HRS) and the Canadian National Population Health Survey (NPHS): 1) describe trajectories of four major health behaviors (physical activity, smoking, alcohol consumption, diet) for up to a 16-year period among middle-aged and older adults (ages 50 years and over) with one of five major chronic illnesses (heart disease, cancer, stroke, respiratory disease, diabetes);2) investigate demographic, socioeconomic, psychological, and health predictors of changes in health behaviors following diagnosis of the illness;3) compare changes in health behavior among U.S. and Canadian patients with chronic disease to understand the role of the health care system. The proposed project will move beyond prior research and address several limitations of existing studies by tracing changes over a extended span of time in a representative sample of middle-aged and older adults, by examining behavior change before and after disease onset, by comparing behavior change among those with and without chronic disease, and by identifying psychosocial and health factors that may be associated with long-term changes in health behavior. By enhancing our understanding of the dynamic changes of health behaviors and identifying the psychosocial, health, and health system characteristics associated with health behavior change among those with chronic conditions, the proposed project will suggest new avenues for interventions and will be instrumental in advancing public health policy regarding chronic disease management. PUBLIC HEALTH RELEVANCE: There have been few studies of long term changes in health behavior following illness and little investigation into the pre-existing factors that may be associated with lifestyle improvements. The proposed study will investigate 14- to 16-year trajectories of change in health behaviors (physical activity, smoking, alcohol consumption, diet) among individuals with chronic health conditions (heart disease, cancer, stroke, respiratory disease, diabetes) in the Health and Retirement Study (HRS) and the Canadian National Population Health Survey (NPHS).